In the manufacture of heat exchangers, one method in common use is to assemble fins on tubes with a loose fit and then expand the tubes to produce a tight fit with the fins and permanently lock the assembly together. This also provides good heat exchange contact between the tubes and the fins.
Generally, expander machines provide a frame having an assembly fixture or nest at one end for holding the loosely assembled tubes and fins and a powered header or ram at the other end. Mounted on the powered ram is a plurality of expander rods aligned with the tubes in the fixture or nest. The ends of the rods are formed with expander ends, or bullets, sized to move along the tube as the ram advances and to expand the tube into tight fitting engagement with the openings in the fins.
One common method of securing the expander rods to the powered header is to insert the rods into selected apertures in the header and rotate the rods 180°, the rods having a half-groove milled into one side of the rod near the upper, tapered end. Therefore, inserting or removing the rods to convert to a different heat exchanger pattern requires each rod to be twisted and removed or, inserted and twisted to secure it in the header. All of this repetitive motion of twisting is done by hand and often results in the repetitive stress injury (RSI) known as carpal tunnel syndrome and also requires additional manufacturing time and effort, thereby increasing manufacturing costs.
Therefore, what is needed is a device and method for securing and removing the expander rods in the header without creating an RSI scenario.